The present invention relates to a silver-silver chloride electrode suitable as an electrode for detecting electrical signals from living bodies and as a standard electrode for measuring electrical characteristics, and the method for manufacturing thereof.
Conventionally, electrodes such as silver, nickel silver, copper and Sunplatina electrodes have been used as sensors to detect low level electrical signals at the skin surface of a living body. These electrodes are not satisfactory since the electrode potential is apt to vary with various secreted substances, temperature and humidity of the environment. Further, the electrodes are easily influenced by external noise. To overcome these problems, non-polarizing electrodes such as silver-silver chloride electrode which are more electrochemically stable than conventional electrodes have recently been used. As a manufacturing method of this electrode, generally a method is used in which silver chloride is deposited by electroplating in a solution containing chlorine ions such as a sodium chloride solution, or another method is used in which silver powder and silver chloride powder are mixed mechanically and then formed by compression. However, the former method has difficulty in manufacture due to the need for very precise plating conditions and long treating time for obtaining an electrode of high performance, as well as the drawback that the resultant silver chloride layer is mechanically brittle and apt to peel off. The latter method has the following drawbacks: Because silver powder and silver chloride powder are mixed in a simple proportion by mere mechanical blending, not only are many process steps such as weighing, blending, pressure-forming, and heat treatment necessary, but also fully homogeneous mixing of both components is not easy due to the difference in specific gravity and particle size, etc., between silver powder and silver chloride powder. This often causes nonuniform local deposition of silver chloride in the porous silver matrix, resulting in unstable quality. The silver powder to be used must be a more expensive reduced silver powder. This reduced silver powder has generally small particle size, tends to cause losses by sticking to the container wall, is cumbersome in handling, and has many problems in manufacture. Furthermore, the heat treatment necessary to obtain an electrode of stable characteristics requires precise temperature control, otherwise the characteristics will fluctuate.